To easily perform adjustment in an easy-to-operate state, when color misregistration due to tilt of a scanning line or misregistrastion in a subscanning direction is caused.

An optical scanner 40 is arranged just under a paper ejection tray 6. An adjusting hole 10 is provided on an external member at a front end of the optical scanner on a front side of the paper ejection tray. An introducing hole 41 is also provided on an upper cover of the optical scanner 40. The adjusting hole 10 is provided at a position (out of a projection range) where it is not superposed on a reading part or a pressure plate (or ADF) existing above the paper ejection tray 6. A tool for adjustment 49 is inserted through the adjusting hole 10, and introduced into the optical scanner 40 through the introducing hole 41 to thereby perform tilt adjustment or resist adjustment by turning an adjusting screw 45.